Are your herbal supplements safe?

It’s been a rough few years for herbs. A Canadian study published late last year found that of 44 herbal products tested, many were adulterated or mislabeled. The study authors said that two samples of echinacea contained a weed that could interact with certain medications; a sample of St. John’s wort was actually an herbal laxative; and a bottle of ginkgo biloba was contaminated with black walnut, which theoretically could put people with nut allergies at risk.

In December, the FDA yanked one herbal supplement from the shelves after it was linked to dozens of cases of liver failure. And a supplement manufacturer who was jailed for selling a weight loss supplement that turned out to contain a toxic chemical is facing new charges over sketchy products he was churning out, even as he was waiting to enter prison.

Though centuries of traditional use and scientific studies point to the therapeutic effects of many medicinal herbs, herbal supplements have always had a potential dark side. Their manufacture isn’t regulated as tightly as that of drugs, creating opportunities for modern-day snake oil salesmen to make a quick buck.

There’s more to the recent exposes and scandals than most media outlets reported. A month-long investigation by Prevention found that the many recent headlines—including “Supplements Are Often Not What They Seem” in the New York Times—emerged from a seriously flawed study. And in the other cases, when supplements were exposed as dangerous, the offending ingredients were not the herbs but other chemicals introduced during manufacture.